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cpufreq: Skip current frequency initialization for ->setpolicy drivers 

After commit da60ce9f2f (cpufreq: call cpufreq_driver->get() after
calling ->init()) __cpufreq_add_dev() sometimes fails for CPUs handled
by intel_pstate, because that driver may return 0 from its ->get()
callback if it has not run long enough to collect enough samples on the
given CPU.  That didn't happen before commit da60ce9f2f which added
policy->cur initialization to __cpufreq_add_dev() to help reduce code
duplication in other cpufreq drivers.

However, the code added by commit da60ce9f2f need not be executed
for cpufreq drivers having the ->setpolicy callback defined, because
the subsequent invocation of cpufreq_set_policy() will use that
callback to initialize the policy anyway and it doesn't need
policy->cur to be initialized upfront.  The analogous code in
cpufreq_update_policy() is also unnecessary for cpufreq drivers
having ->setpolicy set and may be skipped for them as well.

Since intel_pstate provides ->setpolicy, skipping the upfront
policy->cur initialization for cpufreq drivers with that callback
set will cover intel_pstate and the problem it's been having after
commit da60ce9f2f will be addressed.

Fixes: da60ce9f2f (cpufreq: call cpufreq_driver->get() after calling ->init())
References: https://bugzilla.kernel.org/show_bug.cgi?id=71931
Reported-and-tested-by: Patrik Lundquist <patrik.lundquist@gmail.com>
Acked-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
Cc: 3.13+ <stable@vger.kernel.org> # 3.13+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Rafael J. Wysocki 2014-03-12 21:49:33 +01:00
parent fa389e2202
commit 2ed99e39cb
1 changed files with 2 additions and 2 deletions
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4
drivers/cpufreq/cpufreq.c
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@ -1129,7 +1129,7 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif,
per_cpu(cpufreq_cpu_data, j) = policy;
write_unlock_irqrestore(&cpufreq_driver_lock, flags);
if (cpufreq_driver->get) {
if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
policy->cur = cpufreq_driver->get(policy->cpu);
if (!policy->cur) {
pr_err("%s: ->get() failed\n", __func__);
@ -2143,7 +2143,7 @@ int cpufreq_update_policy(unsigned int cpu)
* BIOS might change freq behind our back
* -> ask driver for current freq and notify governors about a change
*/
if (cpufreq_driver->get) {
if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
new_policy.cur = cpufreq_driver->get(cpu);
if (!policy->cur) {
pr_debug("Driver did not initialize current freq");